GT750 Drag Bike

[tz375]

When I did the Superbike school a "few" years ago, someone had bent a school bike and the team just picked it up and slipped a long steel tube through the neck and tweaked it back. That things moved a long way. Our old tube frames are about as stiff as a stick of licorice.

IIRC a downward swingarm droop pulls the rear wheel down under acceleration where a negative droop (wheel higher than pivot) will tend to cause it to rise which might create spin. Without rear suspension the forces are still resolved through the frame tubes and must have some effect, but maybe not much.

It's interesting that custom built drag race frames seem to have swingarms level. That could be because they didn't think about swingarm angles or maybe it's not such a big thing in a rigid chassis or maybe it just works better that way.

[tz375]

Dave is correct with the explanation on how the suspension reacts on a bike with shocks. However on a rigid bike (one with struts like Kevin's) This dynamic is taken out of the picture because the suspension no longer has any movement.
.

My thought is with the GT's flexable frame , the frame itself is acting as suspension . With the wheelie bars and struts attached to the rear of the frame , at launch the frame is " coiling up"just like a spring . i think it was SmokeyAllan that saw this first hand when he was fixing the bent neck on a 72 frame , with a pipe through the steering head he was surprised how easy it was to move the neck around .

That's what we appear to be seeing in that video and in the one where Kevin's hand comes off the bars. the whole frame looks like a big jello wobble. You can almost see waves go through the chassis. One issue here is that the force is unceremoniously dumped into the chassis. It's not a slow gentle effect. It's nothing and then everything in a flash. Zero torque one second and 100 pounds a nano second or so later. I wonder if a higher tech clutch might slow down the shock somewhat so that a shock wave is replaced by a slower wave of longer duration and lower magnitude.

Just thinking out loud again

[Suzukidave]

It's interesting that custom built drag race frames seem to have swingarms level. .

Richard , following up on your thought i pulled up this video .. look at the bikes at :30 and it does look like they are running a neg droop in the setup .. the chain is much more level on the bottom leading me to think the rear wheel is higher than the output sprocket ? I really dont know where i am going with this topic as i have just about ZERO time drag racing or setting up a drag racer .

[water cooled]

SuzDave, try again to post the video. And dont worry about where the topic is going....just know that we are all behind you.

Richard, I had forgotten about the rodeo video until you mentioned it. Now, all I can think about is the frame wobbling like a bowl of jello next time I race. Ill be lucky to hang on at all. Did one of the H2 guys put you up to this?

[Suzukidave]

Yeah .. i guess the link would be nice http://www.youtube.com/watch?v=PCa9q8Ty ... ure=relmfu" onclick="window.open(this.href);return false;

[Suzukidave]

SuzDave, try again to post the video. And dont worry about where the topic is going....just know that we are all behind you.

Richard, I had forgotten about the rodeo video until you mentioned it. Now, all I can think about is the frame wobbling like a bowl of jello next time I race. Ill be lucky to hang on at all. Did one of the H2 guys put you up to this?

If you hadnt posted the slow motion video it would be so easy to miss and riding the beast with all that was going on you probability didnt even feel it .

[tz375]

Kevin, how did you know?

By the time next season comes around you will have perfected a smooth clutch action that makes for a less abrupt force into the frame and you will have looked at where it might work better with a few strategically placed tubes. Plus you'll probably add lock stops to reduce steering angles and add extension straps to the front end.

And you will work out all winter to develop a grip of steel.
The Kawasaki bois won't know what hit them.

[water cooled]

....that's more like it! you crack me up!

[water cooled]

Pic from November 2011 and November 2012 that I found on line from the photographer at Thompson Raceway. Thats my friend Smokin Joe in the first pic, far lane on the ZX12R. Joe is a great racer and good at chassis setup. He was runner up in the S/E National event back in June at Indy. Last month, I retired my Goodyear 5.5 only to find out that GY no longer seems to supply that size or the 7" slick. I switched over to the Mickey Thompson 7" and started the chassis adjustment process over again. The MT slick has slightly different dimensions than GY.



Here is the picture from a couple weeks ago. You can see the radiator is gone, the rear tire is a little bit wider (I am a little thinner) and its too hard to see but the seat has been redesigned. Still have more work to do to get things setup properly.

[Herman T]

Your bike is a mean looking machine Hatchet. The new slick looks great on it also. And yes, you do look a pound or 2 slimmer in the 2nd pic. Kidding of course. The difference is quite noticeable.

[tz375]

looking very professional and purposeful there Kevin.

The front end looks a little tall in those pics. Do the legs need a couple of inches machined out of them or do they need to be strapped down?

[water cooled]

Thanks Gary for the kind words. I hope you get a chance to work on your Buffalo dragbike this winter. 1st race is probably in May or June.

Richard, the bike does sit a little tall in the second picture. If you look close, the throttle is WO and the clutch lever is on its way out but the rear tire isnt wrinkled so I think that the bike was a fraction away from launching. At first, I thought the bike was rising and the forks were telescoping out. Not the case. A racer from the UK spotted that too and recommended a certain strap which I bought and have already installed. Pulls the front end down nice and tight leaving a little suspension but no extension.

[Herman T]

Thanks Gary for the kind words. I hope you get a chance to work on your Buffalo dragbike this winter. 1st race is probably in May or June.

I have to have my dragbike ready for next year because as you know, I want to be on the same run as you when you personally get your first 9 second ET. What a thrill that would be for me!! Time is getting near so I better get things ready.

[water cooled]

The SUPER ELIMINATOR 2013 RACE SCHEDULE was published last night. There are a few on this forum that have expressed some interest and there is certainly growing interest in Suzuki GT Series bikes racing at the strip over the past year or two. The standard bore GT-750 has a slight advantage due to the 738 cc displacement and Index cutoff at 739cc. Anyway, check out the link and click on the 2013 Schedule Tab.

http://www.supereliminator.com/

[D&D CHASSIS]

BUMP?